The impact of shell host (NaYF4/CaF2) and shell deposition methods on the up-conversion enhancement in Tb3+, Yb3+ codoped colloidal α-NaYF4 core-shell nanoparticlesElectronic supplementary information (ESI) available. See DOI: 10.1039/c3nr05412h

• Main Authors: Prorok, Katarzyna, Bednarkiewicz, Artur, Cichy, Bartlomiej, Gnach, Anna, Misiak, Malgorzata, Sobczyk, Marcin, Strek, Wieslaw
• Format: Article
• Language: English
• ISSN: 2040-3364; 2040-3372
• DOI: 10.1039/c3nr05412h

Lanthanide doped, up-converting nanoparticles have found considerable interest as luminescent probes in the field of bio-detection. Although the nanoparticles (NPs) have already been successfully applied for fluorescent bio-imaging and bio-assays, the efficiency of the up-conversion process seems to be the bottle-neck in rigorous applications. In this work, we have shown enhancement of the up-conversion in colloidal α-NaYF 4 :Yb 3+ , Tb 3+ doped nanocrystals owing to passivation of their surface. We have studied quantitatively the influence of the shell type (NaYF 4 and CaF 2 ), its thickness, as well as the shell deposition method ( i.e. single thick shell vs. multi-layer shell) on the luminescent properties of the nanoparticles. The results showed that up to 40-fold up-conversion intensity enhancement may be obtained for the core-shell nanoparticles in comparison with the bare core nanoparticles, irrespective of the shell type and deposition method. Moreover, the suitability of the NaYF 4 :Yb 3+ , Tb 3+ core-shell NPs for multi-color emission and spectral multiplexing has been presented. Schematic illustration of the core-shell nanoparticles synthesis using "shell by shell" or "one step" coating methods.